Add eslint-plugin-compat.

Some new features are obvious, like Promises and fetch, but for some
smaller features we don't always know if they're supported everywhere.
eslint-plugin-compat, however, does :)

It will log an error if we use anything that is not supported in IE 10
or recent versions of Chrome/Edge/Firefox/Safari. Features can be
whitelisted by adding them to the `polyfills` setting in the eslint
config; this is nice, because it gives us an easy list of features that
users may have to polyfill without having to comb through all of the
code!

.browserslistrc

@@ -0,0 +1,8 @@
+IE 10
+last 2 Safari versions
+last 2 Chrome versions
+last 2 ChromeAndroid versions
+last 2 Firefox versions
+last 2 FirefoxAndroid versions
+last 2 Edge versions
+iOS 11.2

.eslintrc

@@ -9,8 +9,12 @@
     "window": true,
     "hexo": true
   },
-  "plugins": ["jest"],
+  "plugins": ["jest", "compat"],
   "rules": {
-    "jsx-quotes": ["error", "prefer-double"]
+    "jsx-quotes": ["error", "prefer-double"],
+    "compat/compat": ["error"]
+  },
+  "settings": {
+    "polyfills": ["fetch", "promises"]
   }
 }

package-lock.json

@@ -5602,6 +5602,65 @@
         }
       }
     },
+    "eslint-plugin-compat": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/eslint-plugin-compat/-/eslint-plugin-compat-2.3.0.tgz",
+      "integrity": "sha1-GNMVzGgymES9VNzBhL5T04pvkcg=",
+      "dev": true,
+      "requires": {
+        "babel-runtime": "^6.26.0",
+        "browserslist": "^3.2.7",
+        "caniuse-db": "^1.0.30000843",
+        "mdn-browser-compat-data": "^0.0.20",
+        "requireindex": "^1.1.0"
+      },
+      "dependencies": {
+        "babel-runtime": {
+          "version": "6.26.0",
+          "resolved": "https://registry.npmjs.org/babel-runtime/-/babel-runtime-6.26.0.tgz",
+          "integrity": "sha1-llxwWGaOgrVde/4E/yM3vItWR/4=",
+          "dev": true,
+          "requires": {
+            "core-js": "^2.4.0",
+            "regenerator-runtime": "^0.11.0"
+          }
+        },
+        "browserslist": {
+          "version": "3.2.8",
+          "resolved": "https://registry.npmjs.org/browserslist/-/browserslist-3.2.8.tgz",
+          "integrity": "sha512-WHVocJYavUwVgVViC0ORikPHQquXwVh939TaelZ4WDqpWgTX/FsGhl/+P4qBUAGcRvtOgDgC+xftNWWp2RUTAQ==",
+          "dev": true,
+          "requires": {
+            "caniuse-lite": "^1.0.30000844",
+            "electron-to-chromium": "^1.3.47"
+          }
+        },
+        "caniuse-db": {
+          "version": "1.0.30000850",
+          "resolved": "https://registry.npmjs.org/caniuse-db/-/caniuse-db-1.0.30000850.tgz",
+          "integrity": "sha1-llyBZkFXbQhwm+4SJWoFUBZLldU=",
+          "dev": true
+        },
+        "caniuse-lite": {
+          "version": "1.0.30000850",
+          "resolved": "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30000850.tgz",
+          "integrity": "sha512-iHK48UR/InydhpPAzgSmsJXRAR925T0kwJhZ1wk0xRatpGMvi2f06LABg6HXfV4WW4P2wChzlcFa/TEmbTyXQA==",
+          "dev": true
+        },
+        "electron-to-chromium": {
+          "version": "1.3.48",
+          "resolved": "https://registry.npmjs.org/electron-to-chromium/-/electron-to-chromium-1.3.48.tgz",
+          "integrity": "sha1-07DYWTgUBE4JLs4hCPw6ya6kuQA=",
+          "dev": true
+        },
+        "regenerator-runtime": {
+          "version": "0.11.1",
+          "resolved": "https://registry.npmjs.org/regenerator-runtime/-/regenerator-runtime-0.11.1.tgz",
+          "integrity": "sha512-MguG95oij0fC3QV3URf4V2SDYGJhJnJGqvIIgdECeODCT98wSWDAJ94SSuVpYQUoTcGUIL6L4yNB7j1DFFHSBg==",
+          "dev": true
+        }
+      }
+    },
     "eslint-plugin-import": {
       "version": "2.8.0",
       "resolved": "https://registry.npmjs.org/eslint-plugin-import/-/eslint-plugin-import-2.8.0.tgz",
@@ -11852,6 +11911,15 @@
       "resolved": "https://registry.npmjs.org/max-safe-integer/-/max-safe-integer-1.0.1.tgz",
       "integrity": "sha1-84BgvixWPYwC5tSK85Ei/YO29BA="
     },
+    "mdn-browser-compat-data": {
+      "version": "0.0.20",
+      "resolved": "https://registry.npmjs.org/mdn-browser-compat-data/-/mdn-browser-compat-data-0.0.20.tgz",
+      "integrity": "sha512-DImQhKtc7umi/LI0licM3GVnKTxYoYmFUKnMjomfIvW8dO4B6UeQLWYQhf1jDTfEV9WZGjFTz3DOfcsnZO6WdA==",
+      "dev": true,
+      "requires": {
+        "extend": "3.0.1"
+      }
+    },
     "media-typer": {
       "version": "0.3.0",
       "resolved": "https://registry.npmjs.org/media-typer/-/media-typer-0.3.0.tgz",
@@ -15483,6 +15551,12 @@
         "resolve-from": "^1.0.0"
       }
     },
+    "requireindex": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/requireindex/-/requireindex-1.2.0.tgz",
+      "integrity": "sha512-L9jEkOi3ASd9PYit2cwRfyppc9NoABujTP8/5gFcbERmo5jUoAKovIC3fsF17pkTnGsrByysqX+Kxd2OTNI1ww==",
+      "dev": true
+    },
     "requires-port": {
       "version": "1.0.0",
       "resolved": "https://registry.npmjs.org/requires-port/-/requires-port-1.0.0.tgz",

package.json

@@ -69,6 +69,7 @@
     "eslint": "^3.19.0",
     "eslint-config-standard": "^10.2.1",
     "eslint-config-standard-preact": "^1.1.6",
+    "eslint-plugin-compat": "^2.3.0",
     "eslint-plugin-import": "^2.8.0",
     "eslint-plugin-jest": "^21.6.2",
     "eslint-plugin-node": "^4.2.3",

src/plugins/GoldenRetriever/.eslintrc.json

@@ -0,0 +1,6 @@
+{
+  "extends": "../../../.eslintrc",
+  "settings": {
+    "polyfills": ["serviceworkers"]
+  }
+}